The research is a systematic study of the contributions of stimulus discriminability and proactive interference to registration-retrieval and retention processes in animal memory. The role of these fundamental factors in memory is being analyzed and measured in an integrated series of experiments using delayed response and delayed matching paradigms. Effects of drugs (principally scopolamine and d-amphetamine) on the principal behavioral components of memory are being assessed, and results are related to effects of the drugs in other, non memory experiments. A series of measures of complex behavior (memory, acquisition, and win/stay-loss/shift) is being used to provide sensitive indications of the behavioral effects of drugs and toxicants. These measures combine the analyzability and interpretability of discrete trial measures of the complex behavior with the sensitivity of free operant measures of intertrial interval performance. An innovative and flexible system is being developed for control of experiments and analysis of data by a TI 980A minicomputer.